Describe the bug
Stack enchanting furnaces break the game

To Reproduce
Steps to reproduce the behavior:
Add fast smelt to any amount of stacked furnace in an anvil.
The stacked furnaces would disappear and instead, would show that that furnace would have double the enchant.

Expected behavior
Something like the hoppers, where they would enchant the entire stack with the same enchant, and each hopper would carry that enchant

Screenshots

Additional context
Add any other context about the problem here.

also, if done multiple times, this action crashes the server. I'm not a server mod so I don't know the specifics entirely, but I'm running v1.7.1 (1.16)

You definitely shouldn't be able to put multiple of the same enchant on one item lol.